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Vehicle Impact Protection

Question
State OH
Description Text

Putting this as simply as possible,  do we think a 32” Jersey Barrier can accomplish the intended goal below? 


Maria E. Ruppe, P.E.

Roadway Standards Engineer

Ohio Department of
Transportation

Mail Stop 1230

1980 W. Broad St.

Columbus, OH 43223

614.466.2847


From: French, Lynn 


Sent: Monday, July 28, 2014 10:38 AM

To: Stargell, Reynaldo

Subject: FW: Vehicle Impact Protection


Hi Reynaldo…


I was referred to you by David
Powers to assist with this question.


Thanks,



Lynn


The Ohio Fire Code (OFC) requires
all aboveground flammable and combustible liquid tanks to be protected from
vehicles using barriers meeting the following code requirement: 


Section
312 Vehicle impact protection


(1)       
312.1 General. Vehicle impact protection required by this code shall be
provided by posts that comply with paragraph (L)(2)(312.2) of this
rule
or by other approved physical barriers that comply with paragraph (L)(3)(312.3)
of this rule.



(2)        312.2
Posts.
Guard posts shall comply with all of the following requirements:



(a)        Constructed
of steel not less than 4 inches (102 mm) in diameter and concrete filled.



(b)        Spaced
not more than 4 feet (1219 mm) between posts on center.



(c)       
Set not less than 3 feet (914 mm) deep in a concrete footing of not less than a
15-inch (381 mm) diameter.



(d)        Set with
the top of the posts not less than 3 feet (914 mm) above ground.



(e)        Located
not less than 3 feet (914 mm) from the protected object.



(3)       
312.3 Other barriers. Physical barriers shall be a minimum of 36 inches
(914 mm) in height and shall resist a force of 12,000 pounds (53 375 N) applied
36 inches (914 mm)
above the adjacent ground surface.


I have quickly looked thru your Roadside Safety Field Guide
and would appreciate if you could help with a variance request we received.


The request is to allow the barriers (jersey barriers
proposed) to be 32” in height in lieu of the required OFC height of 36”.


Any input to these proposed type barriers being equivalent
to the required 36” (3 feet) posts or other barriers would be greatly
appreciated.


Thanks for your input

Keywords
  • Permanent Concrete Barriers
Other Keywords none
Date July 28, 2014


Response
Response

The spec below is specific in terms of height, but not very specific in any other way when regarding the specification for other barrier types. The height is limited to a minimum of 36”. Without further knowledge of the intent of the specification, I don’t believe that we could justify going any lower.

 

In terms of the forces, the spec lists a set load at a height of 36” that the barrier must resist. However it is unclear if the barrier is allowed to deflect or not. Free-standing 32” tall barriers would deflect significantly under that type of load at the top of the barrier and would not be a good fit for this application. Permanent parapets would not deflect appreciably depending on the design, as most of the TL-3 or TL-4 parapet design have withstood crash test impact loads of over 60 kips.

 

Thus, in short, a permanent 36” tall or taller NJ shape, single-slope, or vertical barrier that we use for roadside safety with appropriate anchorage and footing would likely withstand that loading. Vertical barriers would likely be more appropriate for the application as they would produce less vehicle climb and extension and are more typically used in this type of protection scheme.

 

I am not sure if that answers you question. Let me know if you need more information.

Date July 28, 2014


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